This application proposes a continuation of studies designed to evaluate the endocrine response to surgically-induced trauma. Specific studies are designed to measure changes in 24-hour rhythms of plasma cortisol, catecholamine and beta-endorphin concentrations following surgical trauma. We will quantitatively relate alterations in these plasma hormonal patterns with severity of physical insult and events characterizing the pre-, intra and post-operative period of hospitalization. We have developed a collaborative group of research and clinical endocrinologists, research biochemists, surgeons, psychiatrists, psychologists and statisticians and will test the hypothesis that post-surgical alterations in circadian rhythms of endocrine function are related to changes in psychodynamic and physiological parameters induced by events associated with elective surgical procedures. These studies should permit the accomplishment of the following specific objectives: 1) To measure plasma catecholamine and beta-endorphin concentration in pre- and post-surgical conditions and to characterize 24-hour plasma patterns of these hormones. We will determine the degree of rhythmic perturbation of these hormones following surgery. 2) To describe the alteration in the circadian rhythmicity of plasma adrenal hormones and endogenous opiates induced by surgery and measure the rate of return to normal of these rhythms following varying types of surgical trauma. 3) To define and quantitatively describe the post-operative state to include hormone rhythmicity, sleep cycles and psychodynamic parameters in addition to traditional measurements. A series of parameters will be used to describe: 1)the patient's interaction with the hospital milieu and 2) personality characteristics, mood states and psychomotor/cognitive function. We will characterize pre- and post-operative endocrine rhythms, sleep-wake cycles and affective states and correlate them with post-operative recovery patterns. Establishment of an association between these factors may provide a better understanding of the effect of hospitalization and surgery on post-operative adaptive mechanisms and may assist the physician in devising an adequate therapeutic regimen designed to improve and hasten recovery.